Miniaturization of components has increased component and power densities in electronic devices to higher levels than ever before. These electronic and electrical components and devices mounted on printed circuit and wiring boards generate considerable operating heat that, unless dissipated to the environment, may result in temperature related circuit or component failure. Experience has shown that nearly 50% of electronic failures are the result of thermal problems. The generally preferred control method is to use a heat sink to transfer component heat to the surrounding ambient air.
A heat sink can be made of any material with favorable heat transfer characteristics, such as copper, aluminum or steel. Aluminum is generally preferred because it is inexpensive, easy to work with, lightweight, and has good heat transfer characteristics. Where aluminum is used, the less alloying material used in the aluminum, the better the heat transfer characteristics.
The heat sink and heat generating component are usually placed in direct contact with one another in order to more efficiently cool the component. In most cases, after the heat sink absorbs component heat, the heat is transferred to the surrounding ambient air by conduction and convection. A typical printed wiring or circuit board may have a number of heat generating devices. That is why it is not unusual to have a number of heat sinks on a single circuit board associated with heat generating devices and components. Because circuits are frequently enclosed in cabinets or other enclosures, a fan is usually employed to move cooling air across the heat sink and facilitate the transfer of heat.
When a number of heat sinks are required, design factors in addition to temperature control must be taken into consideration. When a printed circuit or wiring board requires multiple heat sinks, the board area occupied by heat sinks will often constitute a significant fraction of the total board space. Similarly, a significant fraction of the total volume available to house a circuit will be taken up by heat sinks when a number of heat sinks are required. As the total area on a board required for heat sinks becomes significant, the board real estate allocated to components also becomes affected by heat sink requirements. Of course, the more efficient heat sink designs will require less area and will be lighter than heat sinks that are not as efficient.
In order to facilitate heat transfer, heat sinks frequently have "fins" to increase the total surface area that serves to conduct and convect heat. These fins typically extend into the flow of air and dissipate the conducted heat into the surrounding ambient air by convection. In most cases, the fins on the heat sink that are located closer to the air flow source will provide for more efficient cooling than those located further away from the air flow source. This is true for a number of reasons, one of which is that air flow to the fins at the leading edge is not blocked, whereas the later fins will be in a dead air zone.
Accordingly, what is needed in the art is a heat sink design that will maximize the efficiency of the heat sink device by permitting the maximum amount of cooling air available to contact the maximum cooling fin surface area of the heat sink in order to provide for more efficient cooling of heat generating devices located in an electronics circuit.